A cash crop is an agricultural crop which is grown for sale to return a profit. It is typically purchased by parties separate from a farm. The term cash crop is applied exclusively to the agricultural production of plants; animal agriculture is not a part of the terminology. The term is used to differentiate marketed crops from subsistence crops, which are those fed to the producer's own livestock or grown as food for the producer's family. In earlier times cash crops were usually only a small (but vital) part of a farm's total yield, while today, especially in the developed countries, almost all crops are mainly grown for revenue. In least developed countries, cash crops are usually crops which attract demand in more developed nations, and hence have some export value.